Process for making beta 3 agonists and intermediates

ABSTRACT

The present invention is directed to a process for preparing a compound of formula I-11 through multiple-step reactions:

TECHNICAL FIELD

The present disclosure relates to a process for making beta 3 agonists and intermediates, ketoreductase (KRED) biocatalysts and methods of using the biocatalysts.

REFERENCE TO SEQUENCE LISTING, TABLE OR COMPUTER PROGRAM

The official copy of the Sequence Listing is submitted concurrently with the specification as an ASCII formatted text file via EFS-Web, with a file name of 3987_0050002_SeqListing.txt, a creation date of Sep. 22, 2017, and a size of 9,935 bytes. The Sequence Listing filed via EFS-Web is part of the specification and is incorporated in its entirety by reference herein.

BACKGROUND OF THE INVENTION

This application is directed to an efficient and economical synthetic process for making a compound of formula I-11 which can be used as an intermediate compound for making beta 3 agonists.

SUMMARY OF THE INVENTION

This application is directed to a multiple-step synthetic process for making a compound of formula I-11. In one embodiment, a KRED enzyme is used in the multiple-step process.

DESCRIPTION OF THE INVENTION

Described herein is a process of making compound I-11 from compound I-1 through multiple step reactions:

wherein R¹ is selected from the group consisting of C₁₋₆alkyl, benzyl and phenyl.

In one embodiment, the multiple-step reactions from compound I-1 to compound I-11 comprise the following steps:

(a) reacting compound I-4:

with an acetonide protection reagent selected from the group consisting of 2,2-dimethoxy propane, 2,2-diethoxylpropane, 2-methoxypropene and acetone, to produce compound I-5:

(b) reducing compound I-5 with a reducing agent at a temperature of 0° C. to 40° C. to produce compound I-6:

(c) oxidizing compound I-6 with an oxidizing agent in the presence of a solvent and a catalyst to produce compound I-7:

(d) reacting compound I-7 with phosphate compound A-4:

to produce compound I-8:

(e) reducing compound I-8 in the presence of a catalyst to produce compound I-9:

(f) reacting compound I-9 with an acid to produce compound I-10:

and

(g) reducing compound I-10 in the presence of a catalyst to produce compound I-11;

wherein P¹ and P² are each independently selected from the group consisting of Ac, Bn, Boc, Bz, Cbz, DMPM, FMOC, Ns, Moz, and Ts; and

R¹ is selected from the group consisting of C₁₋₆alkyl, benzyl and phenyl.

In one embodiment, the solvent in step (c) above is selected from the group consisting of THF, MTBE, CH₂Cl₂, MeCN, toluene and a mixture comprising two of the foregoing solvents. In another embodiment, the oxidizing agent is selected from the group consisting of NaOCl, NaClO₂, hydrogen peroxide, pyridine sulfur trioxide, PCC, and DCC. In another embodiment, the catalyst is TEMPO or a TEMPO analogue.

In one embodiment, the reaction between I-7 and A-4 in step (d) is carried out at a temperature of about 20 to 40° C. In another embodiment, the reaction is carried out in the presence of a solvent selected from the group consisting of THF, MTBE, CH₂Cl₂, MeCN, toluene and a mixture comprising two of the foregoing solvents.

In one embodiment, the catalyst used in the reduction step (e) is selected from the group consisting of Pd, Raney Ni, Pt, PdCl₂, and Pd(OH)₂. In another embodiment, the reduction is carried out in the presence of hydrogen gas.

In one embodiment, the acid in step (f) is selected from the group consisting of HCl, HBr, TFA, MeSO₃H, TfOH, H₂SO₄, para-toluenesulfonic acid, and RSO₃H wherein R is alkyl, aryl or substituted aryl.

In one embodiment, the reduction of step (g) is carried out in the presence of HMDS. In another embodiment, the catalyst used is selected from the group consisting of Pt on alumina, Pd on alumina, Pd/C, Pd(OH)₂—C, Raney Ni, Rh/C, Rh/Al, Pt/C, Ru/C and PtO₂.

In one embodiment, the multiple-step reactions from compound I-1 to compound I-11 further comprise reducing compound I-3:

in the presence of a KRED enzyme to produce compound I-4:

In one embodiment, the KRED enzyme is selected from the group consisting of a polypeptide of SEQ ID NO. 1 and a polypeptide of SEQ ID NO. 2.

In another embodiment, a cofactor recycling system is also present in addition to a KRED enzyme. Suitable cofactor recycling systems include, but are not limited to, a polypeptide of SEQ ID NO. 3 and a polypeptide of SEQ ID NO. 4.

In one embodiment, a KRED enzyme of SEQ ID NO. 1 and a cofactor recycling system of SEQ ID NO. 3 are present in the reduction from I-3 to I-4.

In another embodiment, a KRED enzyme of SEQ ID NO. 2 and a cofactor recycling system of SEQ ID NO. 4 are present in the reduction from I-3 to I-4.

In one embodiment, a cofactor molecule which can donate an electron is also present in addition to a KRED enzyme. In one embodiment, the cofactor is selected from the group consisting of NADH and NADPH.

In one embodiment, the multiple-step reactions from compound I-1 to compound I-11 further comprise reacting compound I-1:

with benzoyl chloride and a protecting reagent to produce compound I-3:

wherein P¹ is a protecting group selected from the group consisting of Ac, Bn, Boc, Bz, Cbz, DMPM, FMOC, Moz, and Ts; and R¹ is C₁₋₆alkyl or an aryl.

In one embodiment, R¹ is methyl, ethyl, propyl or butyl. In another embodiment, R¹ is methyl, ethyl, or phenyl. In one embodiment, P¹ is Boc.

In one embodiment, the conversion from compound I-1 to compound I-3 is carried out through compound I-2:

wherein R¹ is C₁₋₆alkyl or an aryl; and P¹ is selected from the group consisting of Ac, Bn, Boc, Bz, Cbz, DMPM, FMOC, Moz, and Ts.

In one embodiment, the conversion from I-1 to I-3 comprises:

wherein R¹ is C₁₋₆alkyl or an aryl; and P¹ is selected from the group consisting of Ac, Bn, Boc, Bz, Cbz, DMPM, FMOC, Moz, and Ts. In one embodiment, R¹ is methyl or ethyl and P¹ is Boc.

In one embodiment, step (a) or (b) above is carried out in the presence of a base. Suitable bases include, but are not limited to, NaOH, KOH, Na₂CO₃, K₂CO₃, NaHCO₃, K₃PO₄, Et₃N, i-Pr₂Net, and pyridine. In one embodiment, the base is NaHCO₃, Na₂CO₃ or Et₃N.

In one embodiment, the protecting reagent in step (b) is Boc₂O.

In one embodiment, the conversion from I-1 to I-3 is carried out in the presence of a suitable catalyst. In one embodiment, the catalyst is DMAP.

In one embodiment, the conversion from I-1 to I-3 is carried out at a temperature of 0° C. to 60° C., or more specifically, 0° C. to 40° C., or even more specifically, 20° C. to 30° C. In one embodiment, the temperature is 20° C. to 30° C.

In one embodiment, the above conversion from I-1 to I-3 can be carried out using similar synthetic processes as described in Novel N→C Acyl Migration Reaction of Acyclic Imides: A Facile Method for α-Aminoketones and β-Aminoalcohols, Hara, et. al., Tetrahedron Letter, Vol. 39, page 5537 (1998).

In one embodiment, conversion of compound I-3 to compound I-4 is through a dynamic kinetic resolution (DKR) reduction in the presence of a KRED enzyme:

wherein R¹ is C₁₋₆alkyl or an aryl; and P¹ is a protecting group selected from the group consisting of Ac, Bn, Boc, Bz, Cbz, DMPM, FMOC, Moz, and Ts. In one embodiment, R¹ is methyl or ethyl. In one embodiment, P¹ is Boc.

In one embodiment, the enzymatic reduction of I-3 to I-4 is carried out in a solvent. Suitable solvents include, but are not limited to, IPA, DMSO, DMF, DMAc, and combinations thereof. In one embodiment, the solvent is DMSO.

In one embodiment, suitable temperature for the DKR reduction from I-3 to I-4 is 0°-60° C., or more specifically, from 10°-40° C., or even more specifically, from 20°-35° C. In one embodiment, the temperature is about 30° C.

In one embodiment, a KRED enzyme coupled with a cofactor recycling system and an NADPH cofactor is used to reduce compound I-3 to obtain compound I-4. Suitable reaction conditions for the KRED-catalyzed reduction of I-3 to I-4 are provided below and in the Examples.

KRED enzymes belonging to class EC1.1.1.184 are useful for the synthesis of optically active alcohols from the corresponding pro-stereoisomeric ketone substrates and by stereospecific reduction of corresponding racemic aldehyde and ketone substrates.

KRED enzymes typically convert a ketone or aldehyde substrate to the corresponding alcohol product, but may also catalyze the reverse reaction, oxidation of an alcohol substrate to the corresponding ketone/aldehyde product. The reduction of ketones and aldehydes and the oxidation of alcohols by enzymes such as KRED typically require a co-factor, most commonly reduced nicotinamide adenine dinucleotide (NADH) or reduced nicotinamide adenine dinucleotide phosphate (NADPH), and nicotinamide adenine dinucleotide (NAD) or nicotinamide adenine dinucleotide phosphate (NADP+) for the oxidation reaction. NADH and NADPH serve as electron donors, while NAD and NADP serve as electron acceptors. KRED enzymes often can use either the phosphorylated or the non-phosphorylated co-factor.

KRED enzymes can be used in place of chemical procedures for the conversion of different keto and aldehyde compounds to chiral alcohol products. These biocatalytic conversions can employ whole cells expressing the ketoreductase for biocatalytic ketone reductions, or purified enzymes, particularly in those instances where presence of multiple ketoreductases in whole cells would adversely affect the enantiomeric purity and yield of the desired product. For in vitro applications, a co-factor (NADH or NADPH) regenerating enzyme such as glucose dehydrogenase (GDH) and formate dehydrogenase typically is used in conjunction with the ketoreductase.

Examples illustrating the use of naturally occurring or engineered KRED enzymes in biocatalytic processes to generate useful chemical compounds include asymmetric reduction of 4-chloroacetoacetate esters (Zhou, J. Am. Chem. Soc. 1983 105:5925-5926; Santaniello, J. Chem. Res. (S) 1984:132-133; U.S. Pat. Nos. 5,559,030; 5,700,670 and 5,891,685), reduction of dioxocarboxylic acids (e.g., U.S. Pat. No. 6,399,339), reduction of tert-butyl (S)-chloro-5-hydroxy-3-oxohexanoate (e.g., U.S. Pat. No. 6,645,746 and WO 01/40450), reduction pyrrolotriazine-based compounds (e.g., U.S. application No. 2006/0286646); reduction of substituted acetophenones (e.g., U.S. Pat. No. 6,800,477); and reduction of ketothiolanes (WO 2005/054491).

Naturally occurring KRED enzymes can be found in a wide range of bacteria and yeasts (for reviews: Kraus and Waldman, Enzyme catalysis in organic synthesis Vols. 1&2.VCH Weinheim 1995; Faber, K., Biotransformations in organic chemistry, 4th Ed. Springer, Berlin Heidelberg New York. 2000; Hummel and Kula Eur. J. Biochem. 1989 184:1-13). Several KRED gene and enzyme sequences have been reported, including: Candida magnoliae (Genbank Acc. No. JC7338; GI:11360538); Candida parapsilosis (Genbank Acc. No. BAA24528.1; GI:2815409), Sporobolomyces salmonicolor (Genbank Acc. No. AF160799; GI:6539734); Lactobacillus kefir (Genbank Acc. No. AAP94029.1; GI: 33112056); Lactobacillus brevis (Genbank Acc. No. 1NXQ_A; GI: 30749782); Exiguobacterium acetylicum (Genbank Acc. No. BAD32703.1) and Thermoanaerobium brockii (Genbank Acc. No. P14941; GI: 1771790).

The KRED catalyzed reduction of I-3 to I-4 requires that an electron donor is present in the solution. Generally, a cofactor is used as the electron donor in the KRED reduction reaction. The cofactor operates in combination with the KRED and/or GDH in the process. Suitable cofactors include, but are not limited to, NADP⁺ (nicotinamide adenine dinucleotide phosphate), NADPH (the reduced form of NADP+), NAD⁺ (nicotinamide adenine dinucleotide) and NADH (the reduced form of NAD+). Generally, the reduced form of the cofactor is added to the reaction mixture. Accordingly, the methods of the present disclosure are carried out wherein an electron donor is present selected from NADPH cofactor or NADH cofactor. In certain embodiments, the method can be carried out wherein the reaction conditions comprise an NADH or NADPH cofactor concentration of about 0.03-0.5 g/L, about 0.05-0.3 g/L, about 0.1-0.2 g/L, about 0.5 g/L, about 0.1 g/L, or about 0.2 g/L.

In some embodiments of the process, a cofactor recycling system is used to regenerate cofactor NADPH/NADH form NADP+/NAD⁺ produced in the reaction. A cofactor recycling system refers to a set of reactants that reduce the oxidized form of the cofactor (e.g., NADP⁺ to NADPH) thereby allowing the KRED catalysis to continue. The cofactor recycling system may further comprise a secondary substrate and catalyst, for example, the substrate glucose, and the enzyme GDH, that catalyzes the reduction of the oxidized form of the cofactor by the reductant. Cofactor recycling systems to regenerate NADH or NADPH from NAD⁺ or NADP⁺, respectively, are known in the art and may be used in the methods described herein. Suitable exemplary cofactor recycling systems that may be employed include, but are not limited to, glucose and glucose dehydrogenase (GDH), formate and formate dehydrogenase (FDH), glucose-6-phosphate and glucose-6-phosphate dehydrogenase, a secondary (e.g., isopropanol) alcohol and secondary alcohol dehydrogenase, phosphite and phosphite dehydrogenase, molecular hydrogen and hydrogenase, and the like. These systems may be used in combination with either NADP+/NADPH or NAD+/NADH as the cofactor. Electrochemical regeneration using hydrogenase may also be used as a cofactor regeneration system. See, e.g., U.S. Pat. Nos. 5,538,867 and 6,495,023, both of which are incorporated herein by reference. Chemical cofactor regeneration systems comprising a metal catalyst and a reducing agent (for example, molecular hydrogen or formate) are also suitable. See, e.g., PCT publication WO 2000/053731, which is incorporated herein by reference.

In some embodiments of the present disclosure, the cofactor recycling system can comprise glucose dehydrogenase (GDH), which is an NAD⁺ or NADP⁺-dependent enzyme that catalyzes the conversion of D-glucose (dextrose) and NAD⁺ or NADP⁺ to gluconic acid and NADH or NADPH, respectively. GDH enzymes suitable for use in the practice of the processes described herein include both naturally occurring GDHs, as well as non-naturally occurring GDHs. Naturally occurring glucose dehydrogenase encoding genes have been reported in the literature, e.g., the Bacillus subtilis 61297 GDH gene, B. cereus ATCC 14579 and B. megaterium. Non-naturally occurring GDHs generated using, for example, mutagenesis, directed evolution, and the like and are provided in PCT publication WO 2005/018579, and US publication Nos. 2005/0095619 and 2005/0153417.

In some embodiments, the co-factor recycling system can comprise a formate dehydrogenase (FDH), which is an NAD⁺ or NADP⁺-dependent enzyme that catalyzes the conversion of formate and NAD⁺ or NADP⁺ to carbon dioxide and NADH or NADPH, respectively. FDHs suitable for use as cofactor regenerating systems in the KRED catalyzed reaction described herein include naturally occurring and non-naturally occurring formate dehydrogenases. Suitable formate dehydrogenases are described in PCT publication WO 2005/018579. Formate may be provided in the form of a salt, typically an alkali or ammonium salt (for example, HCO₂Na, KHCO₂NH₄, and the like), in the form of formic acid, typically aqueous formic acid, or mixtures thereof. A base or buffer may be used to provide the desired pH.

In some embodiments, the co-factor regenerating system can comprise the same KRED enzyme that catalyzes the reduction of I-3 to I-4. In such an embodiment, the same KRED catalyzing the reduction of I-3 to I-4 also catalyzes the oxidation of a secondary alcohol (e.g., isopropanol to acetone oxidation) and thereby simultaneously reduces the NAD⁺ or NADP⁺ to NADH or NADPH. Accordingly, in some embodiments, the KRED catalyzed conversion of I-3 to I-4 can be carried out in the presence of a secondary alcohol (e.g., IPA) and without any coenzyme (e.g., GDH) present in the solution for the recycling of the NADPH or NADH cofactor. In such embodiments, the suitable reaction conditions can comprise an IPA concentration is about 55-75% (v/v), an NADPH or NADH cofactor loading of about 0.03-0.5 g/L, and wherein no cofactor recycling enzyme is present other than the KRED itself.

Suitable cofactor recycling systems for use in the KRED catalyzed conversion of compound I-3 to I-4 include the co-enzyme glucose dehydrogenase (GDH) coupled with the substrate glucose (L- or D-glucose). Suitable GDH cofactors include, but are not limited to, the GDH of polypeptide of SEQ ID NO. 3 and GDH of polypeptide of SEQ ID NO. 4, both of which are commercially available from Codexis Inc., Redwood City, Calif.

In one embodiment, compound I-5 is prepared by reacting compound I-4 with an acetonide protection agent:

wherein R¹ is selected from the group consisting of C₁₋₆alkyl, benzyl and phenyl; and P¹ is selected from the group consisting of Ac, Bn, Boc, Bz, Cbz, DMPM, FMOC, Ns, Moz, and Ts. In one embodiment, R¹ is selected from the group consisting of methyl, ethyl, propyl, butyl and benzyl. In another embodiment, P¹ is Boc.

Suitable acetonide protection reagents include, but are not limited to, 2,2-dimethoxy propane, 2,2-diethoxylpropane, 2-methoxypropene and acetone. In one embodiment, the acetonide protection reagent is 2,2-dimethoxy propane.

The reaction from I-4 to I-5 can be carried out in the presence of a solvent. Suitable solvents include, but are not limited to, toluene, acetone, THF, IPAc, dichloromethane, EtOAc, MeCN, and mixtures thereof. In one embodiment, the solvent is a mixture of toluene and acetone.

The reaction from I-4 to I-5 can be carried out in the presence of an acid. Suitable acids include, but are not limited to, boron trihalides, organoboranes, HCl, H₂SO₄, TFA, H₃PO₄ and TiCl₄. In one embodiment, the acid is BF₃. In another embodiment, the BF₃ is in the form of boron trifluoride etherate (BF₃.O(Et)₂).

The reaction from I-4 to I-5 can be carried out at a temperature of 10° C. to 50° C., or more specifically, 20° C. to 40° C. It has been found that increasing the reaction temperature from 20° C. to 40° C. can increase the rate of reaction by 2-3 fold while not affecting the product profile.

In one embodiment, compound I-6 is prepared from compound I-5 with a reducing agent:

wherein R¹ is selected from the group consisting of C₁₋₆alkyl, benzyl and phenyl; and P¹ is selected from the group consisting of Ac, Bn, Boc, Bz, Cbz, DMPM, FMOC, Ns, Moz, and Ts. In one embodiment, R¹ is selected from the group consisting of methyl, ethyl, propyl, butyl and benzyl. In another embodiment, P¹ is Boc.

Suitable reducing agents include, but are not limited to, LiAlH₄, LiBH₄, NaBH₄—LiBr and DIBAL. In one embodiment, the reducing agent is LiAlH₄. In another embodiment, the reducing agent is LiBH₄. In yet another embodiment, the reducing agent LiBH₄ can be generated in situ, for example by the use of a combination of NaBH₄ and LiBr.

The amount of the reducing agent is typically 0.8 to 1.6 equiv., or more specifically, 1.0 to 1.4 equiv.

In one embodiment, the reduction from I-5 to I-6 is carried out at a temperature of 0° C. to 60° C., or more specifically, 0° C. to 35° C., or even more specifically, 20° C. to 30° C. In one embodiment, the temperature is 20° C. to 30° C.

In one embodiment, the oxidation of compound I-6 to compound I-7 is carried out in the presence of a catalyst with an oxidizing agent

wherein P¹ is selected from the group consisting of Ac, Bn, Boc, Bz, Cbz, DMPM, FMOC, Ns, Moz, and Ts. In one embodiment, P¹ is Boc.

Suitable oxidizing agents include, but are not limited to, NaOCl, NaClO₂, hydrogen peroxide, Swern oxidation and variants such as pyridine sulfur trioxide, PCC, and DCC. In one embodiment, the oxidizing agent is NaOCl.

The amount of the oxidizing agent is typically 1.1 equiv. to 1.3 equiv., or more specifically, 1.2 equiv. to 1.25 equiv. In one embodiment, the amount of the oxidizing agent is 1.25 equiv.

Suitable catalysts for the above oxidation reaction include, but are not limited to, TEMPO and TEMPO analogues. In one embodiment, the catalyst is TEMPO.

One advantage of the presently described process is that compound I-7 from the oxidation step can be used directly in the next Homer Wadsworth Emmons (hereinafter, “HWE”) step to obtain compound I-8. This one pot process eliminates the need for solvent switch and can increase the yield and reduce cost.

In one embodiment, the oxidation step from I-6 to I-7 can be carried out in the presence of a solvent. Suitable solvents include, but are not limited to, THF, MTBE, CH₂Cl₂, MeCN, toluene and mixtures thereof. In one embodiment, the solvent is a mixture of toluene and MeCN. In another embodiment, the solvent is a mixture of CH₂Cl₂ and MeCN.

In one embodiment, the HWE reaction between I-7 and A-4 is carried out in the presence of a solvent:

wherein P¹ and P² are each independently selected from the group consisting of Ac, Bn, Boc, Bz, Cbz, DMPM, FMOC, Ns, Moz, and Ts. In one embodiment, both P¹ and P² are Boc.

Suitable solvents include, but are not limited to, THF, MTBE, CH₂Cl₂, MeCN, toluene and a mixture comprising two of the foregoing solvents. In one embodiment, the solvent is the mixture of toluene and MeCN.

The HWE reaction is typically carried out at a temperature of −10 to 50° C., or more specifically, 0 to 40° C. In one embodiment, the temperature is 0 to 25° C. In another embodiment, the temperature is 40° C.

The HWE reaction is typically carried out in the presence of a base or a salt. In one embodiment, the base is a tertiary amine. In another embodiment, the base is N,N-diisopropylethylamine (DIPEA).

In one embodiment, the salt is lithium halide, or more specifically, LiCl or LiBr.

In the HWE reaction, an impurity compound I-21 (aldol dimmer by-product) may be formed in addition to compound I-8:

It has been found that by adjusting pH to between 6.5 and 7.0 after the reaction, higher purity compound I-8 can be obtained with improved yield. Additionally, addition of more reactant compound A-4 has been shown to drive the impurity I-21 to product I-8. In one embodiment, addition of an extra 0.2 equiv. of A-4 can reduce the level of I-21 to from 8 LCAP to 2 LCAP.

Increasing the reaction temperature can speed up the conversion to the desired product compound I-8 and reduce the level of the byproduct compound I-21.

By changing the reaction from a batch process to an addition controlled process, the yield of compound I-8 can be improved and the level of byproduct compound I-21 can be reduced. For example, by adding reactant compound I-7 to a solution containing reactant compound A-4, the level of I-21 can be decreased and the yield of compound I-8 improved.

In one embodiment, a solution containing 1.2 equiv of A-4, 3 equiv. of DIPEA and 3 equiv. of LiCl in 5 volumes of MeCN was prepared and warmed to 40° C. A toluene stream of compound I-7 was then added to this mixture over 3 h, after an additional 30 min aging conversion to product was complete. The level of impurity I-21 was about ˜1 LCAP. Sampling the reaction at 1 h intervals showed there was no build-up of compound I-7 in the reaction mixture. After work up the product was isolated with a 90% isolated yield.

It has also been found that using slightly smaller amount of reactant A-4 does not negatively affect the yield of compound I-8. In one embodiment, 1.0 instead of 1.2 equiv. of compound A-4 was used and high yield was still obtained.

Compound A-4 used in the HWE reaction can be prepared from compound A-1:

using similar synthetic steps and conditions as described in A General Procedure for the Preparation of β-Ketophosphonates, Maloney et. al., J. Org. Chem., 74, page 7574-7576 (2009).

In one embodiment, the reduction of compound I-8 to produce compound I-9 is carried out in the presence of a catalyst:

wherein P¹ and P² are each independently selected from the group consisting of Ac, Bn, Boc, Bz, Cbz, DMPM, FMOC, Ns, Moz, and Ts. In one embodiment, both P¹ and P² are Boc.

Suitable catalysts include, but are not limited to, Pd, Raney Ni, Pt, PdCl₂, and Pd(OH)₂. In one embodiment, the catalyst is 5% Pd/C.

In another embodiment, the reduction from I-8 to I-9 is carried out in the presence of a solvent. Suitable solvents include, but are not limited to, THF, MTBE, CH₂Cl₂, MeCN, toluene, methanol, ethanol, 2-propanol and mixtures thereof. In one embodiment, the solvent is THF.

In another embodiment, the reduction reaction is carried out using hydrogen gas at a pressure of 2 to 300 psig, preferably about 40 psig, in the presence of a catalyst.

In one embodiment, compound I-9 reacts with an acid to produce compound I-10 through a cyclization reaction:

Suitable acids include, but are not limited to, HCl, HBr, TFA, MeSO₃H, TfOH, H₂SO₄, para-toluenesulfonic acid, and other sulfone acids such as RSO₃H wherein R is C₁₋₆alkyl, aryl or substituted aryl. In one embodiment, the acid is HCl.

In one embodiment, HCl is used as acid and an HCl salt of compound I-10 is obtained. In one embodiment, the HCl salt is in the form of bis-HCl salt. In another embodiment, the bis-HCl salt is in the form of a mono-hydrate. In another embodiment, the mono-hydrate of the bis-HCl salt of compound I-10 is a crystalline material.

The conversion from I-9 to I-10 can be carried out at a temperature of 0 to 40° C., or more specifically, 15 to 25° C., or even more specifically, 20 to 25° C. In one embodiment, the temperature is 20 to 25° C.

In one embodiment, compound I-10 is reduced to compound I-11 in the presence of a catalyst:

The reaction conditions for the conversion from I-10 to I-11 can be controlled so a cis-selective hydrogenation process is obtained. In one embodiment, the cis-selective hydrogenation is carried out in the presence of a catalyst. Suitable catalysts include, but are not limited to Pt on alumina, Pd on alumina, Pd/C, Pd(OH)₂—C, Raney Ni, Rh/C, Rh/Al, Pt/C, Ru/C and PtO₂. In one embodiment, the catalyst is Pt on alumina.

In another embodiment, the cis-selective hydrogenation from I-10 to I-11 is carried out in the presence of HMDS, which can protect the hydroxy group in situ and therefore improve the diastereo selectivity. Other suitable protecting reagents include, but are not limited to, TMSCl, TESCl, and TBDMSCl.

In one embodiment, compound I-11 is obtained in the form of a crystalline anhydrous free base. In another embodiment, compound I-11 is obtained in the form of a crystalline free base hemihydrate.

As used herein, the term “alkyl” means both branched- and straight-chain saturated aliphatic hydrocarbon groups having the specified number of carbon atoms. For example, C₁₋₆alkyl includes, but is not limited to, methyl (Me), ethyl (Et), n-propyl (Pr), n-butyl (Bu), n-pentyl, n-hexyl, and the isomers thereof such as isopropyl (i-Pr), isobutyl (i-Bu), secbutyl (s-Bu), tert-butyl (t-Bu), isopentyl, sec-pentyl, tert-pentyl and isohexyl.

As used herein, the term “aryl” refers to an aromatic carbocycle. For example, aryl includes, but is not limited to, phenyl and naphthale.

Throughout the application, the following terms have the indicated meanings unless noted otherwise:

Term Meaning Ac Acyl (CH₃C(O)—) Aq Aqueous Bn Benzyl BOC (Boc) t-Butyloxycarbonyl Boc₂O Di-tert-butyl dicarbonate Bz Benzoyl ° C. Degree celsius Calc. or calc'd Calculated Cbz Carbobenzyloxy CDI 1,1′Carbonyldiimidazole DCC N,N′-Dicyclohexycarbodiimide DCM Dichloromethane DKR Dynamic kinetic resolution DMAc N,N-dimethylacetamide DMAP 4-Dimethylaminopyridine DMF N,N-dimethylformamide DMPM 3,4-Dimethoxybenzyl DMSO Dimethyl sulfoxide EDC 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide Eq. or equiv. Equivalent(s) ES-MS and ESI-MS Electron spray ion-mass spectroscopy Et Ethyl EtOAc Ethyl acetate FMOC 9-Fluorenylmethyloxycarbonyl g Gram(s) h or hr Hour(s) HATU O-(7-Azabenzotriazol-1-yl)-N,N,N′,N′- tetramethyluronium hexafluorophosphate HBTU O-(Benzotriazol-1-yl)-N,N,N′,N′- tetramethyluronium hexafluorophosphate) HCl Hydrogen chloride HMDS Hexamethyldisilazane HPLC High performance liquid chromatography HOAc Acetic acid HOBT 1-Hydroxy-1H-benzotriazole HOPO 2-Hydroxypyridine-N-oxide IPA Isopropyl alcohol kg Kilogram(s) LC/MS or LC-MASS Liquid chromatography mass spectrum L Liter(s) LAH or LiAlH₄ Lithium aluminium hydride LCAP Liquid Chromatography Area Percent LiBH₄ Lithium borohydride M Molar(s) Me Methyl MeCN Acetonitrile MeOH Methanol min Minute(s) mg Milligram(s) mL Milliliter(s) mmol Millimole(s) Moz or MeOZ p-Methoxybenzyl carbonyl MTBE Methyl tert-butyl ether NADP Nicotinamide adenine dinucleotide phosphate sodium salt nM Nanomolar Ns 4-Nitrobenzene sulfonyl PCC Pyridinium chlorochromate 5% Pd/C Palladium, 5 weight percent on activated carbon Ph Phenyl r.t. or rt or RT RT Sat. Saturated TBDMSCl Tert-Butyldimethylsilyl chloride TEA or Et₃N Triethylamine TEMPO 1-Oxyl-2,2,6,6-tetramethylpiperidine TESCl Triethylchlorosilane TFA Trifluoroacetic acid THF Tetrahydrofuran TMSCl Trimethylchlorosilane Ts p-Toluene sulfonyl

Reaction Schemes below illustrate the synthetic steps, reagents and conditions employed in the synthesis of the compounds described herein. The synthesis of compound I-11 which is the subject of this invention may be accomplished by one or more of similar routes.

EXAMPLE 1

Preparation of Compound i-11 from Starting Compound i-1

In Scheme 1, one-pot through process produced keto amide i-3 from starting material i-1. An enzymatic DKR reduction produced i-4 from i-3. After protection, ester i-5 was reduced to alcohol i-6 with LAH or LiBH₄.

Once compound i-6 was obtained, it was converted to i-7 by TEMPO oxidation. For the TEMPO oxidation and subsequent HWE coupling step, a one-pot through process was used such that the crude stream of the aldehyde i-7 after phase cut was used directly for the HWE reaction to avoid solvent switch. Unsaturated ketone i-8 was isolated over 5 steps. Finally, compound i-8 was converted to compound i-11 through i-9 and i-10. Detailed experimental conditions are described below.

Step 1. Preparation of Compound i-3 from Compound i-1

To a mixture of Na₂CO₃ (110 g, 1.034 mol) in water (606 mL) and EtOAc (606 mL) at 0-5° C. was added glycine methyl ester (i-1, 119 g, 948 mmol) in portions over 30 min. The resulting slurry was aged for additional 15-30 min, PhCOCl (100 ml, 0.862 mol) was then added dropwise over 1.5 h at 0-5° C. After aging additional 1 h at 0-5° C., the reaction mixture was warmed to 25° C. to form a homonogenous biphasic solution. The separated organic phase was azetropically concentrated and solvent switched to MeCN. A final volume of about 600 mL was obtained.

DMAP (43.1 mmol, 5.26 g) was added and then a solution of Boc₂O (0.948 mol, 207 g) in MeCN (200 mL) was added at RT dropwsie over 2-3 h. The reaction solution was aged at RT for ˜6 h. The batch was vacuum degassed with N₂ three times to remove CO₂ generated in the amidation step. THF (540 mL, KF<500) was added to the reaction solution. A solution of t-BuOK (1.12 mol, 128 g, 97%) in THF (670 ml) was then added at 0-10° C. dropwise over 1-2 h. The reaction solution was aged at 0-5° C. for 1 h.

The reaction was then quenched with 15 wt % citric acid in water (0.431 mol, 91 g citric acid in 515 mL H₂O) at <10° C. The organic phase was washed with 480 mL of half saturated NaCl in water and solvent switched to IPA to a final volume of ˜1.25 L with ˜10% water in IPA at <45° C. The batch was warmed to 40-50° C. Water (1250 mL) was added dropwise at 40-50° C. over 2 h resulting in a slurry.

The slurry was cooled to ambient temperature (20° C.) and aged for 1-2 h before filtration. The wet cake of i-3 was displacement washed with 30% IPA in water (640 mL×2). Suction dry at RT or vacuum oven dry at <50° C. with dry N₂ sweep gave 227 g of white crystalline solid i-3 with 90% yield as determined by HPLC described below.

HPLC Method

Column: Asentis Express C18, 4.6×150 mm, 2.7 am particle size;

Column Temp: 30° C.; Flow Rate: 1.5 mL/min; UV Detection: 210 nm;

Mobile Phase: A: 0.1% H₃PO₄ B: acetonitrile

Mobile Phase Program:

Time, min 0 1 5 7 9 A % 95 95 60 10 10 B % 5 5 40 90 90 Step 2. Preparation of Compound i-4 from Compound i-3 Through DKR Reduction

To a solution of K₂HPO₄ (14.1 g) in 80 mL water at RT was added dextrose (9.8 g) followed by NADP (360 mg), KRED enzyme of SEQ ID NO. 2 (290 mg) and a cofactor recycling system of SEQ ID NO. 4 (115 mg). The resulting homogenous solution was pH adjusted to a minimum of 7.5 with 2M NaOH prior to use.

A solution of i-3 (12.0 g) in DMSO (36 ml) at 30° C. was added dropwise to the above aqueous enzyme solution at 30° C. over 4 h under vigorous agitation. 2M NaOH (˜21 mL) was added dropwise to maintain the reaction mixture at pH of 7.3 to 7.7. Once 90% (˜19 mL) of 2M NaOH solution was added, the reaction temperature was raised to 35° C. until >95% conversion was achieved.

IPA (91 mL) and MTBE (49 mL) were added at RT. The organic layer was separated. The aqueous phase was extracted with IPA/MTBE (140 ml, IPA:MTBE=20:80). The combined organic phase was washed with brine (50 mL, 10% w/v brine) and the crude product containing compound i-4 was directly used for the next step.

Using the following HPLC method, the retention times of i-3 and i-4 were about 8.8 and 7.8 min, respectively.

HPLC Method

Column: Ace 3 Column C18, 3×150 mm, 3 μm particle size

Column Temp: 30° C.; Flow Rate: 0.75 mL/min; UV Detection: 215 nm;

Mobile Phase: A: Formate Buffer, pH 4 (1.26 g HCO₂Na and 0.79 mL HCO₂H in 1 L H₂O)

B: Acetonitrile

Mobile Phase Program:

Time (min) % B 0 5 10 95 Chiral SFC Method Column: Chiralpak IC, 250×4.6 mm, 5 μm particle size Column Temp: 35° C.; Flow Rate: 2 mL/min; UV Detection: 210 nm; Mobile Phase Program:

Time, min 0 2 13 15 A % 95 95 60 60 MeOH % 5 5 40 40 Step 3. Preparation of Compound i-5 from Compound i-4 Through Acetonide Protection

To a toluene solution of the i-4 ester (10.6 g, in ˜25 to 30 mL toluene, crude solution from previous DKR step) were added 50 mL of acetone and 20 ml of 2,2-dimethoxy propane. A solution of BF₃ etherate (0.43 mL) in toluene (2 mL) was then added via a syringe pump at RT over 2 h. The reaction solution was aged at RT for 15 h. The conversion was found to be >97% by HPLC. The retention times of i-4 and i-5 were about 4.5 min and 6.5 min, respectively.

Et₃N (0.5 mL) was added dropwise. After aging for additional 15 min at ambient temperature, the solution was solvent switched to toluene (˜30 mL) while most of the acetone was removed in vacuum. MTBE (60 mL) was added and the organic phase was washed with 5% NaHCO₃/brine (40 mL). Organic phase was azetropically dried and solvent switched to toluene to a final volume of ˜35-40 mL.

HPLC Method

Column: Asentis Express C18, 4.6×150 mm, 2.7 μm particle size

Column Temp: 40° C.; Flow Rate: 1.5 mL/min; UV Detection: 210 nm;

Mobile Phase: A: 0.1% H₃PO₄ B: acetonitrile

Mobile Phase Program:

Time, min 0 5 7 10 A % 95 15 5 5 B % 5 85 95 95 Step 4. Preparation of Compound i-6 Through Reduction of Compound i-5 Compound i-6 can be prepared from the reduction of compound i-5 under two alternative conditions. Option 1: LAH Reduction:

To a crude i-5 ester solution in toluene (8.28 g assay, from previous protection step, in ˜2.5-3 vol of toluene) was added 40 mL of THF. Then, the solution was cooled to 0° C. LiAlH₄ (2M solution in THF, 6.9 mL) was added dropwise over 1 h while the internal temperature was kept at 0-5° C. The reaction solution was aged for additional 0.5-1 h. Conversion was >99% by HPLC. At 0-5° C., 0.52 mL of H₂O in 2.0 mL of THF followed by 0.52 mL of 15% NaOH then followed by 1.56 mL of H₂O were added slowly. The slurry mixture was warmed up to RT and filtrated through Solka Floc. The wet cake was washed with THF (25 mL) and toluene (16 mL).

Assay yield of 91% was obtained using the following HPLC method. The retention times of i-5 and i-6 were about 6.5 min and 5.7 min, respectively.

HPLC Method

Column: Asentis Express C18, 4.6×150 mm, 2.7 μm particle size;

Column Temp: 40° C.; Flow Rate: 1.5 mL/min; UV Detection: 210 nm;

Mobile Phase: A: 0.1% H₃PO₄ B: Acetonitrile

Mobile Phase Program:

Time, min 0 5 7 10 A % 95 15 5 5 B % 5 85 95 95 Option 2: LiBH₄ Reduction

A crude solution of i-5 ester in toluene (11.1 g assay, from previous protection step, in ˜2.5-3 vol of toluene) was added to a mixture of LiBH₄ (0.937 g) in THF (60 mL) over 15-30 min. Then, the reaction solution was aged for 15 h at 35° C. The conversion was >97% by HPLC.

The reaction solution was cooled down to RT and inversely quenched to a solution of 10% NH₄Cl (40 mL) while the internal temperature was maintained below 5° C. with external cooling. The quenched solution was aged at ambient temperature for 2-3 h or until the evolution of H₂ gas ceased. MTBE (100 mL) was added. Aqueous layer was discarded and organic layer was solvent switched to toluene to a final volume of ˜40 mL, which was directly used in the subsequent oxidation step. Assay yield was 92% and aqueous loss was 1.2%.

Step 5. Preparation of Compound i-7 by TEMPO Oxidation of Compound i-6

To a solution of i-6 alcohol in toluene (20 g assay, ˜60 mL) was added acetonitrile (120 mL) at RT. KBr (1.16 g), NaHCO₃ (1.8 g) and water (40 mL) were then charged resulting in a biphasic mixture. The biphasic mixture was cooled to 5° C. and TEMPO (305 mg) was added. Then, NaClO solution (Clorox; 6 wt %; 101 g) was added dropwise at 0-5° C. over 2 h. After addition, the reaction was stirred at 5° C. for ˜30 min. Conversion of >96% was obtained.

The reaction was quenched by dropwise addition of 10% sodium sulfite (50 mL) at 5° C. The organic layer was separated and directly used for the subsequent HWE coupling step without further purification. The assay yield was 17.5 g (88%) by ¹H NMR using DMAc as internal standard.

Retention times of i-6 and i-7 using the following HPLC method were about 3.3 min and 3.9 min, respectively.

HPLC Method

Column: Zorbax, Eclipse Plus C18, 4.6×50 mm, 1.8 μm particle size;

Column Temperature: 22° C.; Flow Rate: 1.5 mL/min; UV Detection: 210 nm;

Mobile Phase: A: 95/5/0.1, H₂O/Methanol/H₃PO₄ B: 95/5, MeCN/methanol

Mobile Phase Program:

Time, min 0 5 6 A % 60 10 10 B % 40 90 90 Step 6. Preparation of i-8 by Homer Wadsworth Emmons (HWE) Coupling Reaction

To a solution of i-7 aldehyde in wet toluene/acetonitrile (162 g solution; 17.5 g assay; 10.81 wt %) obtained above at −10° C. were added acetonitrile (140 mL), phosphonate a-4 (24.6 g) and LiBr (14.9 g) while the internal temperature was maintained below 0° C.

The reaction was warmed up to 0° C., and Hunig's base (22.2 g) was charged at 0-5° C. dropwise over 2 h. The resulting reaction mixture was stirred at 0-5° C. for 2-4 h and allowed to warm to RT, followed by aging at RT for 12 h. HPLC showed conversion (product/(product+aldehyde)) of >99%.

The slurry was cooled to 5° C., and a 10% aqueous solution of citric acid (˜75 g) was added dropwise to adjust the pH to 6.5-7.0 while maintaining the batch temperature at 0-5° C. The aqueous phase was separated at 0-5° C. and discarded.

The organic layer was washed with saturated NaHCO₃ (57 mL) and with H₂O (57 mL) successively. The organic phase was solvent switched to IPA to a final volume of ˜192 mL. The product was gradually crystallized during the distillation.

Water (16.4 mL, 0.6 vol.) was added, and the resulting slurry was heated to 49° C. to give a homogeneous solution. The resulting solution was cooled to 40° C. and seeded (0.27 g). The resulting mixture was aged at 40° C. for 2 h to establish a seed bed, and H₂O (93 mL) was charged dropwise at 40° C. over 3 h, followed by aging at 40° C. for 1 h. The slurry was allowed to cool to 5-10° C. over 2 h, followed by aging at 5-10° C. for 2 h.

The wet cake was washed with 50% H₂O/IPA (a 164 mL cold displacement wash followed by a 110 mL slurry wash). Suction dried under nitrogen gave the product as an off-white solid (24.9 g, 100 wt %, >99 LCAP, 80% isolated yield from aldehyde).

Using the following HPLC method, the retention times of i-7, a-4 and i-8 were about 3.0 min, 1.2 min and 3.8 min, respectively.

HPLC Method

Column: Zorbax, Eclipse Plus C18, 4.6×50 mm, 1.8 μm particle size

Column Temp: 40° C.; Flow Rate: 1.5 mL/min; UV Detection: 210 nm;

Mobile Phase: A: 0.1% H₃PO₄ B: MeCN

Mobile Phase Program:

Time, min 0 3 7 A % 60 10 10 B % 40 90 90 Step 7. Preparation of Compound i-9 from Compound i-8

THF (84 g) followed by enone i-8 (19.07 g) and 10% Palladium on carbon (0.95 g) were charged to a hydrogenation vessel. The batch was hydrogenated for 90 min at 25° C. until uptake of hydrogen had ceased. The catalyst was removed through filtration of a bed of solka floc. The filtered residues were washed with THF (84 g). The combined organic phase was solvent switched to IPA to a final volume of 142 mL, which was directly used in the next step. Assay yield of 93% was obtained (17.8 g of i-9).

Using the following HPLC method, the retention times of i-8 and i-9 were about 11.2 min and 11.4 min, respectively.

HPLC Method

Column: HiChrom ACE C18 (250×4.6 mm), 3 μm particle size;

Column Temperature: 30° C.; Flow rate: 1.0 mL/min; Detection: 210 nm, 254 nm;

Mobile phase: A: 1 mL of phosphoric acid (85%) dissolved in 1 L of H₂O B: MeCN

Mobile Phase Program:

Time, min 0 5 8 15 16 20 A % 95 65 5 5 95 95 B % 5 35 95 95 5 5 Step 8. Preparation of Compound i-10 from Compound i-9

To a solution of the N-Boc-Ketone aniline i-9 (26.1 assay kg) in IPA (˜125 g/L) was added 4N HCl in IPA (220.8 L) at RT. The reaction mixture was stirred vigorously at 20-25 ° C. for 24 h. The batch was distilled under reduced pressure, at constant volume by charging IPA up to one batch volume, to remove HCl. The batch was then concentrated to a final volume of ˜215 L.

The resulting slurry was heated to 45° C., and IPAc (˜430 L) was slowly added to the batch over 2-3 h. The slurry was then cooled to ˜20° C. over 1-2 h and aged overnight. The batch was filtered, and the cake was washed with a 1:2 mixture of IPA:IPAc (52 L) followed by IPAc (52 L). The wet cake was dried at 45° C. under nitrogen atmosphere to give the cyclic imine bis-HCl monohydrate salt i-10 (16.1 kg). The isolated yield of 94% was obtained.

Using the same HPLC method as in Step 7 (i-8 to i-9), the retention times of i-9 and i-10 (bis-HCl salt) were about 11.3 min and 8.3 min, respectively.

Step 9. Preparation of Compound i-11 from Compound i-10

To a mixture of imine dihydrochloride monohydrate i-10 (12.0 g, 98.5 wt %) in THF (86 mL) under N₂ was added hexamethyldisilazane (10.95 g) while maintaining the batch temperature below 25° C. The resulting slurry was stirred vigorously at ambient temperature for 2 h.

A 300 mL autoclave was charged with a suspension of 5% platinum on alumina (0.605 g) in THF (32 mL), followed by the substrate slurry prepared above. The resulting mixture was stirred at RT under hydrogen (40 psig) until the hydrogen uptake ceased. The completion of the hydrogenation was confirmed by HPLC, and the vessel was inserted with nitrogen.

The reaction mixture was discharged, and the vessel rinsed with 96 mL of THF. The batch was filtered through a pad of Solka Floc, and the pad was rinsed with the THF vessel rinse (˜96 mL). The combined filtrate was stirred with 0.5 M hydrochloric acid (129 mL) at ambient temperature for 1 h. The aqueous layer was separated. IPAc (39 mL) followed by 5 N sodium hydroxide (˜15 mL) was added to adjust the pH to 10.0 with vigorous stirring.

The organic layer (˜120 mL) was separated and treated with AquaGuard Powder (Meadwestvaco) (2.4 g) at RT for 2 h. The solution was filtered through a pad of Solka Floc, and the pad was rinsed with 2-propanol (18 mL). The combined filtrate was concentrated to 70 mL. The solution was distilled at the constant volume by feeding a total of 140 mL of 2-propanol, maintaining the batch temperature at 33-35° C. The resulting solution was concentrated to ˜34 mL and heated to 50° C., followed by addition of H₂O (6.3 mL). The resulting solution was cooled to 41-43° C. and seeded with pyrrolidine aniline hemihydrate (42 mg). The resulting mixture was aged at 41-43° C. for 1 h to establish a seed bed.

Water (60.9 mL) was charged at 41-43° C. over 6 h, and the resulting mixture was allowed to cool to 10° C. over 3 h, followed by aging at 10° C. for 2 h. The solids were collected by filtration and washed with 25% 2-propanol/H₂O (50 mL). The wet cake was suction-dried at ambient temperature under nitrogen to afford 7.68 g of pyrrolidine aniline i-11 as hemihydrate.

¹H NMR (d₆-DMSO) δ 7.27 (m, 4 H), 7.17 (m, 1 H), 6.81 (d, J=8.1, 2 H), 6.45 (d, J=8.1 Hz, 2H), 5.07 (s, br, 1 H), 4.75 (s, 2 H), 4.18 (d, J=7.0 Hz, 1 H), 3.05 (m, 2 H), 2.47 (dd, J=13.0, 6.7 Hz, 1 H), 2.40 (dd, J=13.0, 6.6 Hz, 1 H), 1.53 (m, 1 H), 1.34 (m, 1 H0, 1.22 (m, 2 H).

¹³C NMR (d₆-DMSO) δ 146.5, 144.3, 129.2, 127.8, 127.4, 126.8, 126.7, 114.0, 76.8, 64.4, 60.1, 42.1, 30.2, 27.2.

Using the following HPLC method, the retention times of i-10 (bis-HCl salt) and i-11 were about 8.3 min and 8.5 min, respectively.

HPLC Method

Column: Waters Xbridge C18, 150×4.6 mm, 3.5 μm;

Column Temperature: 25° C.; Flow rate: 1 mL/min; Detection: 210 nm, 254 nm;

Mobile phase: A: Acetonitrile B: 0.1% aqueous NH₄OH adjusted to pH9.5 with H

Mobile Phase Program:

Time, min 0 4 8 10 17 A % 99 65 65 30 30 B % 1 35 35 70 70

EXAMPLE 2

Preparation of Compound i-8 from Compound i-1—Alternative Conditions

Step 1. Preparation of Compound i-3 from Compound i-1

To an inserted 1000 L vessel, water (178 kg) was charged, followed by glycine methyl ester hydrochloride (HCl salt of i-1, 35.0 kg) to form a solution. EtOAc (178 L; 160.6 kg) was charged and the mixture cooled to 0° C. Triethylamine (56.4 kg; 78 L) was added over about 30 min maintaining internal temperature <10° C. The mixture was cooled to 0° C. and benzoyl chloride (35.6 kg; 29.4 L) added over >30 min maintaining internal temperature <10° C. HPLC analysis at the end of the benzoyl chloride addition showed 100% conversion to benzoylated intermediate.

10% Phosphoric acid (prepared from 9 kg of 85 wt % phosophoric acid and 81 kg H₂O) was then charged over 15 min and the mixture stirred. The lower aqueous layer was removed and then back-extracted with EtOAc twice (178 L; 160.6 kg followed by 89 L; 80.3 kg). Loss to aqueous layer was about 2.1%.

The organic layers were combined and concentrated to ˜50 L, then acetonitrile (178 L; 140.0 kg) charged and concentrated to ˜50 L. Acetonitrile (178 L; 140.0 kg) was then charged and the solution cooled to 0° C. and DMAP (3.09 kg) charged. Cooling to 0° C. was required to remain below the flash point of MeCN before charging solid via manway.

The mixture was warmed to 20° C. and a solution of Boc anhydride (60.8 kg; 64.7 L) in MeCN (64.7 L; 60.8 kg+10 L rinse) was charged to the mixture over 30 min. The reaction mixture was aged overnight. HPLC analysis showed 100% conversion to Boc-intermediate.

The mixture was degassed via 3×vacuum/N₂ cycles, cooled to 0° C. and a solution of t-BuOK (36.9 kg) in THF (142 L; 126.6 kg) added over 1 h maintaining internal temperature <5° C. The reaction mixture was aged for 1 h at 5-10° C. HPLC analysis showed full conversion to keto-ester.

10% Citric acid (aq.) (prepared from 36.5 kg citric acid and 328.6 kg H₂O) was then added to the mixture, stirred and the lower aqueous layer removed.

5% NaCl (aq.) (prepared from 14.25 kg NaCl and 270.8 kg H₂O) was added to the organics, stirred and the lower aqueous layer removed. The lower brine layer was back-extracted with MTBE (80 kg) and all organics combined.

The combined, washed organics were concentrated to ˜300 L, then IPA (178 L; 139.7 kg) added and concentrated down to ˜285 L (1H-NMR showed no residual MeCN) then IPA (117 kg) added. The slurry was heated to 50° C. to obtain a solution and H₂O (327.5 kg) added over 1 h maintaining internal temperature at 40-50° C., then cooled to 20° C. over 45 min and aged overnight. Liquor loss was <2% by end of the cool-down.

The slurry was filtered and washed with IPA/H₂O (38.3 kg: 146.3 kg) and the solids dried overnight at 50° C. in vacuo to give ketoester compound i-3 as an off-white solid (65.25 kg; 99.4 LCAP; 100 LCWP) The yield was 89%.

Using the HPLC method described below, the retention time of i-3 was about 4.0 min.

HPLC Method

Column: Ascentis Express C18, 100×4.6 mm, 2.7 m particle size;

Column Temperature: 40° C.; Flow rate: 1.8 mL/min; Detection: 210 nm, 220 nm, 254 nm;

Mobile phase: A: 1.0 ml of 99.9% phosphoric acid (85 w/w %) in 1 L of H₂O B: MeCN

Gradient:

Time, min 0 6 8 9 10 A % 90 5 5 90 90 B % 10 95 95 10 10 Step 2. Preparation of Compound i-4 from Compound i-3 Through DKR Reduction

A 0.1M phosphate buffer solution was prepared by dissolving sodium phosphate dibasic dihydrate (8.54 kg) in water (480 kg). The pH was adjusted to 7.0 using HCl (approx 1.5 L).

0.1M phosphate buffer (400 kg) was charged to a 1000 L vessel followed by DMSO (66 kg). D-(+)-glucose (39.2 kg) and NADP disodium salt (0.90 kg) was charged via the manway and the mixture stirred at 30° C. until all solids had dissolved.

The remaining 0.1M phosphate buffer (88.5 kg) was charged to a 400 L vessel, followed by the KRED enzyme of SEQ ID NO. 1 (3.0 kg) and a cofactor recycling system of SEQ ID NO. 3 (0.30 kg). This mixture was stirred slowly at 20° C. until all enzymes had dissolved. Violent stirring should be avoided to prevent form from forming in the mixture. Once dissolved, a hazy yellow solution was obtained.

To a 160 L vessel was charged the keto ester substrate i-3 (32.6 kg) followed by DMSO (66 kg). The mixture was stirred at 30° C. until all the solid had dissolved.

The pH of the glucose/NADP solution was adjusted from 7.19 to 7.50 using 2M sodium hydroxide solution (2.4 kg).

The enzyme solution was then transferred to the 1000 L vessel, followed by a water line wash (5 kg). The pH of the combined solution was then re-adjusted from 7.30 to 7.50 by the addition of 2M sodium hydroxide solution (1.9 kg).

The DMSO solution of the keto ester was then charged to the 1000 L vessel over approximately 4 h, maintaining the temperature in the reaction vessel at 30° C. and maintaining the pH between 7.3 and 7.7.

Starting material crystallized during addition. Reaction mixture was then a slurry throughout. The pH became more acidic as the reaction progressed. The range of 7.3 to 7.7 was maintained by the addition of 2M NaOH.

The reaction was then aged at 30° C., with the pH maintained between 7.3 and 7.7 until reaction was complete. Reaction achieved 90% completion after approximately 5 days. Total uptake of 2M NaOH was 55 kg. Projected total uptake was 60 kg.

The extraction workup was performed in two halves due to vessel volume limitations. The amounts detailed below are for the total batch size.

MTBE (900 L) and methanol (400 L) were charged and the mixture stirred and allowed to settle. A two phase mixture was obtained—upper clear organic layer containing the product and a lower hazy aqueous layer containing all of the enzyme residues. Separation was good but did require a 30-60 min settling time.

The phases were separated and the aqueous extracted with MTBE (300 L). The organic phases were combined and washed with 10% brine (150 L). Total losses to aqueous layers were 1-2% of theory yield.

The organic layer was then concentrated from 1100 L to 95 L by distillation at reduced pressure. Toluene (185 kg) was charged and the batch concentrated to a final volume of 100 L. Batch temperature maintained below 40° C. during distillation.

Total material processed was 64.2 kg. Assay yield was 53.9 kg (86%). Contained ˜14% keto ester i-3. ee >99.9%. KF<250 ppm. MTBE not detected by 1H NMR.

Using the HPLC method described below, the retention times of i-3 and i-4 were about 4.5 min and 3.8 min, respectively.

HPLC Method

Column: Ascentis Express C18, 100×4.6 mm, 2.7 μm particle size;

Column Temperature: 40° C.; Flow rate: 1.8 mL/min; Detection: 210 nm;

Mobile phase: A: 1.0 ml of 99.9% phosphoric acid (85 w/w %) in 1 L of H₂O B: MeCN

Gradient:

Time, min 0 6 8 A % 90 5 5 B % 10 95 95 Step 3. Preparation of Compound i-5 from Compound i-4 Through Acetonide Protection

To an inserted 1000 L vessel, the hydroxyester i-4 in toluene (53.9 kg hydroxyester; total solution 114.1 kg) was charged, followed by acetone (257 L; 203 kg) and 2,2-dimethoxypropane (97 L; 82 kg) and the mixture stirred for 5 min. Boron trifluoride diethyl etherate (2.20 L; 2.47 kg) was charged to the mixture over 30 min and aged 15 h overnight at 20° C. (no exotherm was noted). Reaction time was ˜4 h for completion; HPLC analysis after overnight showed >99% conversion.

Triethylamine (2.4 L; 1.76 kg) was then charged and the mixture concentrated to low volume (˜100 L). MTBE (308 L; 229 kg) was charged, followed by 5% NaHCO₃ (aq.) (129 L prepared from 6.45 kg NaHCO₃ and 122.55 kg H₂O) and 10% NaCl (aq.) (129 L prepared from 12.9 kg NaCl 116.1 kg H₂O). The mixture was stirred for 5 min, the layers allowed to settle and the lower aqueous layer removed. The washed organics were concentrated to ˜75 L, then toluene charged (91 L; 105 kg) and concentrated to ˜75 L. Toluene (138 L; 119 kg) was then added. Reaction time was ˜4 h for completion; HPLC analysis after overnight showed >99% conversion.

Triethylamine [2.4 L; 1.76 kg] was then charged and the mixture concentrated to low volume, ˜100 L. MtBE [308 L; 229 kg] was charged, followed by 5% NaHCO₃ (aq.) [129 L prepared from 6.45 kg NaHCO₃ and 122.55 kg DI H₂O] and 10% NaCl (aq.) [129 L prepared from 12.9 kg NaCl 116.1 kg DI H₂O]. The mixture was stirred for 5 min., the layers allowed to settle and the lower aqueous layer removed. The washed organics were concentrated to ˜75 L, then toluene charged [91 L; 105 kg] and concentrated to ˜75 L. Toluene [138 L; 119 kg] was then added.

Final solution was 176.8 kg and product acetonide i-5 assay was 61.2 kg (100%). Keto ester compound i-3 was still present at 14.2 LCAP.

Using the same HPLC method as in Step 1 of this Example, the retention times of i-4 and i-5 were about 3.2 min and 5.2 min, respectively.

Step 4. Preparation of Compound i-6 Through Borohydride Reduction of Compound i-5

To a 1000 L vessel was charged tetrahydrofuran (218 kg) and 10% lithium borohydride solution in THF (50.8 kg). The mixture was stirred and the temperature adjusted to 20° C.

A solution of acetonide ester i-5 (containing ˜14 LCAP keto ester i-3 carried through from the enzymatic DKR step) in toluene (55.9 kg of substrate in a total of 176.8 kg of toluene solution) was charged over 45 min maintaining the batch temperature between 20 and 25° C. The batch was warmed to 35° C. and aged for 18 h. Small exotherm was noted during charging of substrate. Minimal off-gassing was observed. HPLC showed <1% starting material remaining.

The batch was transferred to a 400 L vessel followed by a THF line wash (10 kg). To the 1000 L vessel was charged a solution of ammonium chloride (24.5 kg) in water (245 kg). The ammonium chloride solution was cooled to 0-5° C. and then the batch charged over 90 min, maintaining the temperature between 0 and 5° C. Hydrogen gas evolved. Rate of addition of batch to ammonium chloride quench solution was controlled so as not to pressurise vessel.

The quenched reaction mixture was warmed to 20° C. and stirred for 2 h (until off-gassing ceased). Agitation was stopped and the layers allowed to settle. The lower aqueous phase was run out and the organic washed with ˜10% brine (5 kg sodium chloride in 50 kg water). There was some emulsion at interface and so the majority of the organics were removed and the emulsion and aqueous layer re-extracted with toluene (100 kg). The organic phases were combined and concentrated at reduced pressure to 100 L (batch temperature maintained below 40° C.).

Heptane (410 kg) was charged and the mixture warmed to 30° C. The batch was washed with a mixture of acetonitrile (20 kg) in water (300 kg) for 20 min. The aqueous layer was removed and the wash repeated twice more. Washing performed at 30-35° C. to maintain solubility. Diol compound i-16 which has the following structure was reduced from 14 to 2 LCAP:

The organic phase was then concentrated to 100 L under reduced pressure. Acetonitrile (120 kg) was charged and the batch concentrated to 140 L (142 kg). Assay yield was 55.6 kg (99%) and <2 LCAP of i-16 was present.

Using the same HPLC method as in Step 2 of this Example, the retention times of i-5, i-6 and i-16 diastereomers were about 5.6 min, 4.9 min, 3.0 min and 3.1 min respectively.

Step 5. Preparation of Aldehyde Compound i-7 by TEMPO Oxidation of Compound i-6

To an inserted 1000 L glass-lined vessel were charged KBr (2.65 kg), NaHCO₃ (4.11 kg) and water (152 kg). The toluene/CH₃CN/heptane solution of the alcohol i-6 (142 kg at 39.2 wt %) was added to the aqueous solution, followed by acetonitrile (83 kg) and toluene (153 kg). The resulting stirred solution was cooled to 0-2° C. Using a diaphragm pump, a solution of TEMPO (0.695 kg) in toluene (2.8 L) was added to the reaction mixture, rinsing the line and pump with toluene (˜1 L).

Using an air-driven Teflon-lined pump, sodium hypochlorite (120 kg, 99 L, 13.9 wt % active chlorine) was charged to the vessel through an above-surface addition line. The sodium hypochlorite solution was then added to the reaction mixture over a period of 70 min while maintaining the batch temperature below 10° C. The addition-line was rinsed into the batch with water (1 kg). The batch was aged at <5° C. for 20 min. The sodium hypochlorite does not need to be pre-cooled to 15° C., but should not be at temperatures above ambient (i.e. 23° C.). The addition rate should be maintained within 60-70 min. A longer addition rate will incur larger amounts of both starting material and over-oxidized acid by-product, whilst a shorter run time will probably not be possible due to exothermic activity. The exotherm will cease as soon as addition of the bleach stops. In this case, 4.0 LCAP starting material, 1.3 LCAP acid and 87.4 LCAP aldehyde was obtained. A further 0.05 eq. NaOCl (4 kg) was charged before proceeding with the quench, although the batch was not re-assayed again.

The temperature of the batch was checked at 5° C., and 1 M sodium sulfite (total prepared from 5.04 kg of Na₂SO₃ and 35 kg water; actual amount added was only 18 L of this solution) was then added over a period of 10 min, maintaining the batch temperature below 10° C. The batch temperature was set to 20° C. and aged for 5 min. The batch was tested with starch iodide paper to ensure no oxidant was present.

The bi-phasic mixture was mixed for 10 min and then allowed to settle out. The lower aqueous layer was removed and disposed of. The top organic cut was washed with water (68 kg). The lower aqueous cut as again removed and disposed of. The organic layer was again tested for oxidant with starch iodide paper. (Good hold point-hold solution at 5° C.).

Both cuts were very good and settled fairly quickly. The final organic cut indicated 1.3 LCAP starting material and 91.1 LCAP aldehyde. In both aqueous layers, residual KBr and the acid by-product were removed.

The organic solution was then distilled, under vacuum, to a final volume of ˜135 L whilst maintaining temperature <40° C. (˜3 volumes based on yield of aldehyde). KF should be <2% water for the subsequent HWE step. In this case the KF was 80 μg/mL.

This afforded a 36.8 wt % solution of aldehyde (131.7 kg total; 36.8 wt %, 48.5 kg assay for i-7; 87% yield (¹H-NMR assay with anisole as internal standard), which was stored in a plastic lined steel drum under nitrogen at 5° C. whilst awaiting further processing. Using the HPLC method described below, the retention times of i-6 and i-7 were about 4.9 min and 5.5 min, respectively.

HPLC Method

Column: Ascentis Express C18, 100×4.6 mm, 2.7 μm particle size;

Column Temperature: 40° C.; Flow rate: 1.5 mL/min; Detection: 210 nm, 254 nm;

Mobile phase: A: 1.0 ml of 99.9% phosphoric acid (85 w/w %) in 1 L of H₂O B: MeCN

Mobile Phase Gradient:

Time, min 0 5 7.5 7.51 A % 90 10 10 90 B % 10 90 90 10 Step 6. Preparation of i-8 by HWE Coupling of i-7 Aldehyde with Compound a-4

The phosphonate a-4 (67.4 kg, 1.2 equiv.) and lithium chloride (19.98 kg, 3 equiv.) were charged to a 1000 L vessel, followed by acetonitrile (188.64 kg). The mixture was cooled to ˜5° C. and N,N-Diisopropylethylamine (60.95 kg, 3 equiv.) was added while maintaining an internal temperature below 20° C. Once addition was complete the batch was warmed to 40° C. and the solution of aldehyde i-7 in toluene from the previous step was added over 3 h then aged for a further 30 min.

Adding the aldehyde solution to the prepared ylide resulted in a very low level (˜1 LCAP) of aldol dimmer by-product I-21 at the end of the reaction:

The batch was cooled to 0° C. and MTBE (177.6 kg) was added followed by citric acid (10% aq.) to adjust the pH to between 6.5 and 7 (6.87 achieved in the plant). If the pH was overshot then addition of 2N NaOH was conveniently used to adjust the pH back into range.

The aqueous lower layer was run off and the organics were washed with 10% sodium bicarbonate solution (240 L), then water (2×120 L). During the first aqueous wash there was some solid in the aqueous layer identified as citric acid salts precipitated due to super saturation. This was conveniently ran off with the aqueous layer.

An assay yield of the final solution showed there was 75.67 kg, 90.1% in the organic stream (Note: this was an estimate based on approximate volume in the vessel) Losses to the aqueous cuts were <0.1%.

The solution was distilled to a minimum volume (˜100 L) and iso-propyl alcohol (604.5 kg) was added. The solution was then distilled to a final volume of 616 L (˜7 volumes+product), and the batch was heated to 49° C. Water (46.2 kg, 0.6 volumes) was added and the batch was cooled to 40° C. over 30 min. The batch was seeded and allowed to age for 1 h at 40° C. to establish a seed bed. Water (492.8 kg) was then added to the batch over 1 h whilst marinating the batch temperature at 40° C. The batch was aged for 2 h at 40° C. then cooled to 10° C. over 2 h, and aged at this temperature over night. After the age period an assay of the liquors showed there was a liquor concentration of 2.9 mg/ml. The batch was filtered and the cake was washed with 1:1 of IPA:water (380 L) which had been cooled to 10° C. The solid was dried in vacuo at 40° C. Then co-milled to afford 75.93 kg of the desired product, 100 LCAP, 99 wt %, 89% yield. Losses to the liquors and washes were 3%.

With the success of this protocol the reaction was attempted using only 1.01 equiv of phosphonates a-4, this resulted in a 99% assay yield at the end of reaction.

Using the same HPLC method as in Step 2 of this Example, the retention times of a-4 and i-8 were about 3.8 min and 6.2 min, respectively.

Using procedures similar to Steps 7-9 of Example 1, compound i-11 can be prepared from compound i-8.

While the invention has been described and illustrated with reference to certain particular embodiments thereof, those skilled in the art will appreciate that various changes, modifications and substitutions can be made therein without departing from the spirit and scope of the invention. It is intended, therefore, that the invention be defined by the scope of the claims which follow and that such claims be interpreted as broadly as is reasonable. 

What is claimed is:
 1. A process for producing compound I-10:

comprising: (a) oxidizing compound I-6:

to produce compound I-7:

(b) reacting said compound I-7 with phosphonate compound A-4:

to produce compound I-8:

(c) reducing said compound I-8 to produce compound I-9:

 and (d) reacting said compound I-9 with an acid to produce compound I-10:

wherein said P¹ and said P² are each independently a protecting group.
 2. The process of claim 1, wherein in step (a) said oxidizing is carried out with an oxidizing agent in the presence of a solvent and a catalyst; said solvent is selected from the group consisting of tetrahydrofuran (THF), methyl tert-butyl ether (MTBE), dichloromethane (CH₂Cl₂), acetonitrile (MeCN), toluene and a mixture comprising two of said foregoing solvents; said oxidizing agent is selected from the group consisting of sodium hypochlorite (NaOCl), sodium chlorite (NaClO₂), hydrogen peroxide, pyridine sulfur trioxide, pyridinium chlorochromate (PCC), and N,N′-dicyclohexycarbodiimide (DCC); and said catalyst is 1-oxyl-2,2,6,6-tetramethylpiperidine (TEMPO) or a TEMPO analogue.
 3. The process of claim 1, wherein said reaction between said compound I-7 and said compound A-4 in step (b) is carried out at a temperature of 20 to 40° C. and in the presence of a solvent selected from the group consisting of tetrahydrofuran (THF), methyl tert-butyl ether (MTBE), dichloromethane (CH₂Cl₂), acetonitrile (MeCN), toluene and a mixture comprising two of the said foregoing solvents.
 4. The process of claim 1, wherein in step (c) said reducing is carried out in the presence of a catalyst and hydrogen gas; and said catalyst is selected from the group consisting of Pd, Raney Ni, Pt, PdCl₂, and Pd(OH)₂.
 5. The process of claim 1, wherein said acid in step (d) is selected from the group consisting of HCl, HBr, trifluoroacetic acid (TFA), MeSO₃H, TfOH, H₂SO₄, para-toluenesulfonic acid, and RSO₃H, wherein R is an alkyl, an aryl or a substituted aryl.
 6. The process of claim 1, wherein said P1 and said P2 are each independently selected from the group consisting of acyl (Ac), benzyl (Bn), t-butyloxycarbonyl (Boc), benzoyl (Bz), carbobenzyloxy (Cbz), 3,4-dimethoxybenzyl (DMPM), 9-fluorenylmethyloxycarbonyl (FMOC), 4-nitrobenzene sulfonyl (Ns), p-methoxybenzyl carbonyl (Moz), and p-toluene sulfonyl (Ts).
 7. The process of claim 1, further comprising: reacting compound I-4:

wherein said R¹ is selected from the group consisting of C₁₋₆alkyl, benzyl, and phenyl, with an acetonide protection reagent selected from the group consisting of 2,2-dimethoxy propane, 2,2-diethoxylpropane, 2-methoxypropene and acetone, to produce compound I-5:

 and reducing said compound I-5 with a reducing agent to produce said compound I-6:


8. The process of claim 7, wherein said reducing said compound I-5 is carried out at a temperature of 0° C. to 40° C.
 9. The process of claim 7, wherein said R¹ is C₁₋₆alkyl.
 10. The process of claim 7, further comprising: reducing compound I-3:

in the presence of a ketoreductase (KRED) enzyme to produce said compound I-4:


11. The process of claim 10, wherein said R¹ is C₁₋₆alkyl.
 12. The process of claim 10, wherein said KRED enzyme is an enzyme having EC number 1.1.1.184.
 13. The process of claim 10, wherein said KRED enzyme is derived from Candida magnoliae, Candida parapsilosis, Sporobolomyces salmonicolor, Lactobacillus kefir, Lactobacillus brevis, Exiguobacterium acetylicum, or Thermoanaerobium brockii.
 14. The process of claim 10, wherein said KRED enzyme comprises an amino acid sequence selected from the group consisting of the amino acid sequence of SEQ ID NO: 1 and the amino acid sequence of SEQ ID NO:
 2. 15. The process of claim 14, further comprising a cofactor recycling system comprising an amino acid sequence selected from the group consisting of the amino acid sequence of SEQ ID NO: 3 and the amino acid sequence of SEQ ID NO:
 4. 16. The process of claim 15, further comprising a cofactor selected from the group consisting of NADH and NADPH.
 17. The process of claim 10, further comprising: reacting compound I-1:

with benzoyl chloride and a protecting reagent to produce said compound I-3:


18. The process of claim 17, where said R¹ is C₁₋₆alkyl.
 19. A process for producing compound I-10:

 comprising: (a) reacting compound I-1:

with benzoyl chloride and a protecting reagent to produce compound I-3:

(b) reducing said compound I-3 in the presence of a ketoreductase (KRED) enzyme to produce compound I-4:

(c) reacting said compound I-4 with an acetonide protection reagent selected from the group consisting of 2,2-dimethoxy propane, 2,2-diethoxylpropane, 2-methoxypropene and acetone, to produce compound I-5:

(d) reducing said compound I-5 with a reducing agent to produce compound I-6:

(e) oxidizing said compound I-6 with an oxidizing agent in the presence of a solvent and a catalyst to produce compound I-7:

(f) reacting said compound I-7 with phosphonate compound A-4:

to produce compound I-8:

(g) reducing said compound I-8 in the presence of a catalyst to produce compound I-9:

 and (h) reacting said compound I-9 with an acid to produce compound I-10:

wherein said P¹ and said P² are each independently selected from the group consisting of acyl (Ac), benzyl (Bn), t-butyloxycarbonyl (Boc), benzoyl (Bz), carbobenzyloxy (Cbz), 3,4-dimethoxybenzyl (DMPM), 9-fluorenylmethyloxycarbonyl (FMOC), 4-nitrobenzene sulfonyl (Ns), p-methoxybenzyl carbonyl (Moz), and p-toluene sulfonyl (Ts); and said R¹ is selected from the group consisting of C₁₋₆alkyl, benzyl, and phenyl.
 20. The process of claim 19, wherein said R¹ is C₁₋₆alkyl.
 21. The process of claim 19, wherein said KRED enzyme in step (b) comprises an amino acid sequence selected from the group consisting of the amino acid sequence of SEQ ID NO: 1 and the amino acid sequence of SEQ ID NO:
 2. 22. The process of claim 21, wherein step (b) further comprises a cofactor recycling system comprising an amino acid sequence selected from the group consisting of the amino acid sequence of SEQ ID NO: 3 and the amino acid sequence of SEQ ID NO:
 4. 23. The process of claim 22, further comprising a cofactor selected from the group consisting of NADH and NADPH. 